1. Field of the Invention
The present invention relates to a method and apparatus for multiplexed decoding of bar codes and symbols using a hand-held symbology reader.
2. Description of the Related Art
Bar codes are linear symbols that encode textual strings or data that are used in industrial applications to identify parts or components and/or characteristics and features of the parts or components upon which they are applied. In an application that employs the use of a bar code symbol, a device is used to “read” the bar code and decode the encoded data. In applications like part tracking and warehouse operations, the act of reading a bar code is a means for data entry that is fast, consistent, and reliable.
Two-dimensional symbols have been developed as an extension to linear bar codes to provide a high density symbol with capabilities to encode significantly more information. For example, the Data Matrix symbol is a commonly-known two dimensional symbol that encodes data within a matrix of cells that occupy a two-dimensional grid. Two-dimensional codes are also referred to as stacked or matrix codes.
Reading devices have been developed to read one-dimensional bar codes that have been optimized for extremely fast response times. These readers are typically laser scanning systems that project a laser illumination onto the targeted bar code symbol to produce a reflectance waveform that is detected and rapidly analyzed by the reading device. These systems, however, are not easily adapted to reading symbols that have data encoded in more than one dimension.
Image-based readers have been developed to read two-dimensional symbols. In these image-based systems, an acquired image is processed and analyzed using machine vision algorithms to find the symbol in the image, and through the implementation of symbol decoding algorithms, the symbol is decoded.
While laser scanning one-dimensional bar code readers are not suitable for reading two-dimensional codes, image based two-dimensional readers are quite adaptable for decoding both one-dimensional bar codes and two-dimensional symbols. An image-based reader configured to read a one-dimensional code can locate and decode a bar code with a response time that is substantially similar to a laser-scanning reader. However, when an image-based reader is configured to perform autodiscrimination (automatically determine if either a one-dimensional symbol or a two-dimensional symbol is being read), the effective response time can be drastically and unacceptably increased.